The present invention relates to an apparatus and a method for controlling a target distance and a warning distance between two traveling vehicles and a recording medium for storing the control method.
To improve the safety in a vehicle driving operation and reduce the driver""s burden, an apparatus for automatically controlling a distance between two traveling vehicles is conventionally proposed. According to the conventional automatic distance control, the vehicle speed is controlled so as to equalize an actual distance between two traveling vehicles with a target distance. The target distance is usually constant. It may be possible to set the target distance to be variable in accordance with the present vehicle speed. In such a case, the target distance remains constant whenever the vehicle speed is constant.
The automatic distance control is performed by controlling a physical quantity directly representing a distance itself or indirectly representing the distance, such as a time interval between two vehicles. The time interval is obtained by dividing the distance between two vehicles by the vehicle speed of the system""s vehicle.
When the target distance is fixed to a constant value, the drive feeding is worsened in various conditions.
An object of the present invention is to provide an apparatus and a method for controlling a distance between two traveling vehicles which is capable of adjusting a target distance between the two traveling vehicles in accordance with the driving conditions.
An object of the present invention is to provide an apparatus and a method for judging and generating a warning in accordance with the driving conditions.
An object of the present invention is to provide a recording medium for storing a computer program relating to the distance control and warning control realized by the present invention.
According to an aspect of the present invention, a physical quantity is detected as a value directly or indirectly representing an actual distance between the two traveling vehicles. A distance control is performed so as to maintain a target distance between the two traveling vehicles based on the detected physical quantity. A temporary distance control is performed to suppress a deceleration degree of a succeeding vehicle to a smaller value compared with a deceleration degree attainable during an ordinary distance control when the two traveling vehicles are departing from each other under a condition where the actual distance between the two traveling vehicles is already shorter or will soon become shorter than a standard target distance.
According to a preferable embodiment of the present invention, a control value is obtained based on a first physical quantity and a second physical quantity. The first physical quantity represents a distance deviation between an actual distance and a target distance between two traveling vehicles. The second physical quantity represents a relative speed between the two traveling vehicles. The succeeding vehicle is accelerated and/or decelerated based on the obtained control value to adjust the actual distance between the two traveling vehicles. The temporary distance control is performed to suppress the deceleration degree of the succeeding vehicle when the two traveling vehicles are departing from each other under a condition where the actual distance between two traveling vehicles is shorter than the standard target distance.
Preferably, the automatic distance control of the present invention is performed by a microcomputer. It is judged whether an objective in a present control cycle is identical with an objective in a previous control cycle of the distance control. And, the temporary distance control for suppressing the deceleration degree of the succeeding vehicle is performed only when the preceding vehicle is judged to be the same objective in the present and previous control cycles of the distance control.
Preferably, the target distance is temporarily changed to a provisional target distance to realize the temporary distance control for suppressing the deceleration degree of the succeeding vehicle. The provisional target distance has an initial value substantially equal to the actual distance between the two traveling vehicles and a transitional value gradually restoring to the standard target distance.
According to another preferable embodiment of the present invention, the control value is obtained based on the first physical quantity and the second physical quantity to accelerate or decelerate the succeeding vehicle based on the obtained control value in the same manner. The temporary distance control is performed when the actual distance between two traveling vehicles is shorter than the standard target distance.
Preferably, the target distance is changed to a provisional target distance which has an initial value determined in accordance with the relative speed between the two traveling vehicles and a transitional value gradually restoring to the standard target distance.
Preferably, the initial value of the provisional target distance is expressed by a decreasing function of the relative speed in a region between a predetermined negative value and a predetermined positive value of the relative speed. The initial value is equal or closer to the standard target distance when the relative speed is smaller than the predetermined negative value, and is equal or closer to the actual distance between the two traveling vehicles when the relative speed is larger than the predetermined positive value.
Alternatively, the initial value of the provisional target distance is expressed by a decreasing function of the relative speed in a region between a first positive value and a second positive value of the relative speed, where the second positive value is larger than the first positive value. The initial value is equal or closer to the standard target distance when the relative speed is smaller than the first positive value, and is equal or closer to the actual distance between the two traveling vehicles when the relative speed is larger than the second positive value. In both cases, the relative speed is a positive value when the two traveling vehicles are departing from each other and is a negative value when approaching to each other.
According to another preferable embodiment, the control value is obtained based on the first physical quantity and the second physical quantity to accelerate or decelerate the succeeding vehicle based on the obtained control value in the same manner. The temporary distance control is performed when the actual distance between the two traveling vehicles is already shorter or will soon become shorter than the standard target distance due to an intentional driver""s operation of the succeeding vehicle performed to reduce the actual distance between the two traveling vehicles.
Preferably, the intentional driver""s operation of the succeeding vehicle is a lane change operation of the succeeding vehicle performed to follow up a new objective traveling on another traffic lane which is faster than the succeeding vehicle.
Preferably, the intentional driver""s operation of the succeeding vehicle is an override operation performed to manually accelerate the succeeding vehicle so as to approach the preceding vehicle.
Preferably, the intentional driver""s operation of the succeeding vehicle is a control startup operation performed to start the distance control.
The temporary distance control may be performed only when the relative speed between two traveling vehicles is larger than a predetermined value.
Preferably, the target distance is temporarily changed to a provisional target distance which has an initial value substantially equal to the actual distance between the two traveling vehicles and a transitional value gradually restoring to the standard target distance.
Alternatively, the target distance has an initial value determined in accordance with the relative speed between the two traveling vehicles and a transitional value gradually restoring to the standard target distance. In this case, the initial value of the provisional target distance is expressed by a decreasing function of the relative speed in a region from a negative lower value to an upper value equal to or closer to 0. The initial value is equal or closer to the standard target distance when the relative speed is smaller than the negative lower value, and is equal or closer to the actual distance between the two traveling vehicles when the relative speed is larger than the upper value.
For example, when the intentional driver""s operation of the succeeding vehicle is the lane change operation, it is preferable to set the upper value to be a positive value closer to 0.
When the intentional driver""s operation of the succeeding vehicle is the override operation, it is preferable to set the upper value to be a negative value closer to 0.
When the intentional driver""s operation of the succeeding vehicle is the control startup operation, it is preferable to set the upper value to be a negative value closer to 0.
According to the present invention, the control variable is not limited to the distance between the two traveling vehicles. In this respect, it is preferable to use a target acceleration.
According to another preferable embodiment of the present invention, the temporary distance control is performed by setting a target acceleration of the succeeding vehicle. The deceleration degree of the succeeding vehicle can be temporarily suppressed to the smaller value by changing a lower limit of the target acceleration to a provisional level. The provisional level has an initial value higher than an ordinary level and a transitional value gradually restoring to the ordinary level.
According to another preferable embodiment of the present invention, a warning operation is performed when the actual distance between the two traveling vehicles becomes shorter than a predetermined warning distance. And, a temporary warning control is performed for setting a provisional warning distance shorter than an ordinary warning distance when the actual distance between the two traveling vehicles is already shorter or will soon become shorter than the ordinary warning distance due to the intentional driver""s operation of the succeeding vehicle performed to reduce the actual distance between the two traveling vehicles.
Preferably, the provisional warning distance has an initial value substantially equal to the actual distance between the two traveling vehicles and a transitional value gradually restoring to the ordinary warning distance.
Preferably, the succeeding vehicle has a plurality of deceleration devices being independently operable and different from each other in degree of attainable deceleration. And, at least one of the plurality of deceleration devices is selected to decelerate the succeeding vehicle. Furthermore, the warning operating is prohibited when a deceleration level attainable by the selected one or plurality of deceleration devices is lower than a predetermined maximum level even if the actual distance between the two traveling vehicles is shorter than the ordinary warning distance.
In this case, the deceleration level of the succeeding vehicle is judged to be higher than the predetermined maximum level when a deceleration device capable of generating a largest deceleration is selected to decelerate the succeeding vehicle, or when a predetermined combination of deceleration devices capable of generating a largest deceleration is selected to decelerate the succeeding vehicle, or when the control value is equivalent to an available maximum deceleration.
For example, the temporary warning control is performed when the intentional driver""s operation of the succeeding vehicle is the lane change operation, the override operation, or the control startup operation. The temporary warning control may be canceled when the succeeding vehicle is approaching the new objective.
It is preferable to perform the distance control and the warning control of the present invention by the microcomputer. The control program for executing the distance control and the warning control is stored in a recording medium which is installable in a computer system.